If you want to choose a concrete additive to gain strength, you’ll find that it’s a little more complicated than just picking a material and mixing it in. There are additives you can choose which will result in either short or long-term strength gains in your cured concrete. However, making concrete is more like baking a cake than making some trail mix. Every ingredient impacts one another, down to how much water you need to mix it. It is best to talk to professionals about which specific mix will work for your uses. However, we can give you some basic guidance on ways to make your concrete stronger.
The Basics of Concrete Strength
What makes concrete strong in the first place? If what you care most about is strength, then the ideal concrete:
- Has a lower water content
- Has high-quality, small aggregates (gravel, stone, sand, and geosynthetics are options)
- Has a low amount of air mixed in
- Has reinforcements such as steel
While this is a good starting point, there are additives which you can add to concrete to make it stronger. Just remember that you need to balance strength with other characteristics such as durability, workability, cure time, cost and more.
Concrete Retarders
Retarder additives are about slowing down the time that it takes for your concrete to set. This can be important for large projects where you need the concrete to be workable for longer. If you want to set a pattern into the concrete but don’t have time to do that before it sets, it is common to add a surface retarder. While it reduces initial strength, the longer cure for concrete retarders can increase strength over the long term.
Concrete Accelerators
Concrete accelerators are additives which are meant to speed up the set time of your concrete. They are often necessary when installing concrete in cold weather, as they prevent frost damage to the concrete. In the short term, the concrete will be stronger. However, long term, concrete with an accelerator is of lowered strength compared to the same mixture without it.
Concrete Superplasticizers
Superplasticizers are the additives that let us make high-strength concrete. They allow us to significantly reduce the amount of water we put in the concrete without impacting the flow and workability. With lower water content, these concrete types are stronger. There is a very wide range of superplasticizers. They are expensive options and are often incompatible with one another—so you need to be selective about their use and careful about mixing them. They also slow down the curing time of the concrete.
Supplementary Cementitious Materials
These are extra materials which can add all kinds of properties to the cement that you’re using. The specific characteristics will depend on the specific material that you use, but adding strength is possible. Some of the supplementary cementitious materials you can use for strength include:
- Silica fume: This is a pozzolanic material created as a by-product of the creation of silicon. It adds strength and significantly reduces the ability of water to permeate the concrete.
- Fly ash: This material can add strength, but the source matters.
We can help you select the right additives for your concrete.
